Fuel supply system for internalcombustion engines



P 7, 1948. ca. J. ARMSTRONG 4 FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTIONENGINES Filed Feb. 27, 1945 4 Sheets-Sheet 1 I9 FIGZI.

32 33 D Z l8 3/ 3O a as L za II I In venlor A ttorney April 27, 1948. G.J. ARMSTRONG 2,

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTiON ENGINES Filed Feb. 27, 1945 4Sheets-Sheet 2 Pas/r1 v p/sPLA CEMENT PUMP In uenlor p i 1948.- G. J.ARMSTRONG 2, 40,

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 27, 1945 4Sheets-Sheet 3 16 F IG .3.

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m 35 130 2 I 34 E a E DUE L 12 E 1 I I Pas/77: 5 fi/J'PLHCEME/YT 10 P000Inventor A Home y April 1948. G. J. ARMSTRONG 2,

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES 4 Sheets-Sheet 4 Filed Feb. 27, 1945 II 1 68/ n w:

D/Sfll. n cane/v 7' pump Inventor By 2 Attorney Patented Apr. 27, 1948UNITED STATES PATENT OFFICE FUEL SUPi'LY SYSTEM FOR INTERNAL- GOMBUSTIONENGINES George Jefl'rey Armstrong, Farnborougli, England ApplicationFebruary 27, 1945, Serial No. 580,029 In Great Britain June 26, 1943 6Claims. (Cl. 123-119) The invention relates to fuel supply systems forreciprocating internal combustion engines in which fuel is injected intoan intake manifold along which air is passing to the engine. It is knownthat in such systems the mass air consumntion, i. e, the air consumptionmeasured in units of mass per unit time, and hence the 1 mosphericpressure, and hence atmospheric.

pressure may be measured instead of exhaust back pressure to .controlthe fuel flow. More particularly the invention relates to such a systemin which the flow of fuel is controlled by an adjustable metering valveor valves whose effective flow area is adjusted in accordance with theintake manifold pressure, atmospheric or exhaust back pressure, and itis an object of the invention to provide a means for controlling thepressure difference across-the metering valve or valves by an adjustablepressure-reducing valve which regulates said pressure difference inaccordance with the square of the engine speed whereby for a givenadjustment of the meterin valve or valves the flow through said meteringvalveor valves is' made dependent on the engine speed.

In accordance with the invention in a system of the kind hereinbeforespecified, the output of a positive displacement pump driven at a speedproportional to engine speed is passed through a passage having apressure-reducing constriction, e. g. a sharp edged orifice, and thepressure difference across said constriction is applied to a pressureresponsive element which actuates the pressure reducing valve; It willbe appreciated that since the flow from a positive displacement pump isproportional to the speed at which the pump is driven, the pressuredifference at the two sides of the constriction will be proportional tothe square of the engine speed and hence the pressure-reducingvalve willbe adjusted in accordance with the square of the engine speed so thatfor a given adjustment of the metering valve or valves the desiredproportionality between flow through the metering valve and engine speedwill be maintained.

ments, one of said elements being exposed to the i 2 pressure differenceacross the constriction and the other to the pressure difference acrossthe metering valve or valves, so that the pressure reducing valve iscontinuously adjusted to provide a relationship between the two pressuredifferences, which relationship is determined by the I relative areas ofthe two diaphragms or the like.

The invention is illustrated in the accompanying schematic drawings, inwhich:

Fig. 1 is a sectional view of a system embodying the invention and alsoincorporating the invention of co-pending British application No.9250/43 (U. S. Serial No. 580,028).

. Fig. 2 is a fragmentary sectional view showing an alternative means ofintroducing temperature correction,

Fig. 3 is a fragmentary sectional view showing an alternative diaphragmassembly,

Figs. 4 and 5 are views showing alternative arrangements each having twopositive displace- Conveniently, the positive displacement pump mentpumps connected in series.

Referring to Fig. 1 fuel passes through pipe Ill to a positivedisplacement pump ll driven by a shaft ill from the engine 21a to whichfuel is to be supplied, said shaft i ll being the engine accessorydriving shaft. From the pump II the fuel is supplied to the enginethrough a sharpedged orifice l2, passage 13, chamber ll, pressurereducing valve l5, chamber l6, metering valve l'l, passage l8, chamberl9 and discharge nozzle 20. whose effective area is adjusted by atapering needle 2| connected to a link 22 pivoted at 23 to the wall of achamber 24 and connected to a link to which are attached resilientbellows 25, 26, bellows 25 being subject internally to the pressure inthe intake manifold 21 of the engine 21a, 9. connecting pipe 28 beingprovided for this purpose, and bellows 26 being evacuated internally.The inside of chamber 24 communicates with the passage l8 through a port29 and is filled with fuel in which both bellows are immersed. The fuelin the passage l8 and consequently in the chamber 24 is maintained at apressure exceeding atmospheric by a predetermined amount by a taperingneedle 30 which co-operates with the discharge nozzle 20 and which isanchored to a The valve ll comprises an orifice I'I forms no part of thepresent invention and that the present invention may be embodied insystems employing other means for producing such adjustment. The presentinvention is concerned .with the regulation of the pressure differenceacross the metering orifice I1, and this means will now be described.

The engine driven pump H is arranged to have an output exceeding themaximum fuel requirements of the engine at any engine speed. and to,

provide for conditions in which the fuel requirements are less than theoutput of the pump H a spring-loaded relief valve 34 is providedpreferably of balanced type. The whole of the output of the pump II ispassed through the orifice I2 and the relief valve 34 is accordinglylocated on the output side downstream of the orifice l2. Since theoutput of the pump II is proportional to the engine speed, the pressuredifference across the orifice I2 is proportional to the square of saidspeed. A tapping 35 is led from the high pressure side of the orifice I2 to chamber 36 sealed by a flexible diaphragm 31 the righthand side ofwhich is acted upon by the pressure existing in the chamber 4, i. e. thepressure at the low pressure side of the orifice l2. The diaphragm 31 isconsequently blessed by the pressure difference across the orifice I2.Connected to the diaphragm 31 is one end of a link 38 carrying atapering plug 39 which forms the adjustable member of the pressurereducing valve I5. The link 38 is also connected through a pivoted lever40 to a further link 4| carried by a second diaphragm 42. The pressureat the left hand side of the diaphragm 42 is that existing in thechamber l6, 1. e. the pressure immediately upstream of the meteringvalve I! while at the right hand side of the diaphragm 42 the pressureexisting is that immediately downstream of the metering valve, a port 43being provided to admit such pressure to the right hand side ofdiaphragm 42. Accordingly, when the system is operating, the pressuredifference across the orifice i2 applies to the diaphragm 31 a forceproportional to the square of the engine speed, and this force istransmitted through the link 33, lever 40 and link 4| to the diaphragm42 and the pressure reducing valve I5 is thus so adjusted that the flowthrough the valves causes the forces applied by the diaphragms 31 and 42to be in equilibrium. Such equilibrium will exist when the pressuredifferences across the two diaphragms achieve a relationship which isdetermined by the relative areas of the diaphragms and the relativeeffective lengths of the arms of the lever". The Dressure differenceacross the metering orifice I! will therefore be maintained proportionalto the square of the engine speed. Temperature control may be introducedin a variety of ways, thus in the form illustrated, a bulb 44 filledwith liquid is located in the intake manifold 21 and is connected by acapillary tube 45 to a. capsule 46 one end of which is fixed and theother end of which is connected to a pivoted arm 41 on which the lever40 is mounted. Movement of the capsule in response to changes intemperature in the intake manifold will displace the pivot of the lever4|! in relation to the links 38, 4| to which it is connected and willaccordingly vary the relationship between the effective lengths of thearms of the lever 40 and hence the ratio between the square of theengine speed and the pressure difference across the metering orifice.

The system also embodies a slow running device in which fuel from thechamber I4 is fed to passage l8 past a tapered plug 48 anchored to adiaphragm 49, the two sides of which are exposed to the pressures offuel in the chambers 36 and I4 and on which a tension spring 30 acts tohold the plug 48 away from its seating. As

the engine speed increases the pressure difference across the diaphragm49 rises overcoming the resistance of the tension spring 50 anddiminishing the flow of fuel through the slow running device.

Referring to Fig. 2. temperature correction is produced by varying theeffective area of the oriicel2 instead of by varying the effectivelengths of the arms of the lever 40. For this purpose a tapered needle63 is pivoted to one end of a pivoted arm 6|, the other end of which ismoved by a Bourdon tube 62 or like element which responds to changes oftemperature in the intake manifold. 1

Other alternative means of introducing temperature correction arepossible, e. g. any of the means described in co-pending Britishapplication No. 9250/43. If the temperature correction is eflected asshown in Fig. 2 or as in British application No. 9250/43, the capsule 46shown in Fig. 1 may be retained and made responsive to some othervariation for which it is desired to correct or vary the fuel-air ratio.Thus if the capsule 46 were evacuated the pressure difference across themetering valvell would become pro portional not to the square of theengine speed but to apower of the engine speed differing from the squarethereof.

Referring now to Fig. 3, fuel from pump I after passing through theorifice I2 is supplied to the engine through passage I3, pressurereducing valve l5, metering valve II and passage IS. The effective flowpassage of the metering valve I1 is varied by a tapered needle 2| whichmay be operated by means not shown but which may be analogous to thoseshown in Fig. 1. The means for adjusting the pressure reducing valvehowever diifers from that shown in Fig. 1. As illustrated in Fig. 3 thepressure reducing valve comprises a tapered plug 39 attached to a link38 secured to four diaphragms, 3H, 31, I31 and 3'. Between diaphragms3|! and 31 is a chamber 36 communicating with the upstream sideoforifice l2 through a passage 35, while the space I40 betweendiaphragms 3|! and I3! communicates with the downstream side of theorifice |2 through passage I311. The pressure at the right hand side ofdiaphragm 3H is the same as that at the upstream side of the meteringvalve I1, while the space between the diaphragms l3'l'and 3' is filledwith fuel at the pressure existing at the downstream side of valve l1,said pressure being transmitted through port 29, chamber 24 and balancetube I24. Diaphragms 3|1 and I3! are in the nature of flexible walls thefluid forces on which are balanced one against the other by design andin particular by the inclusion of a duct H3. The system willconsequently be in equilibrium when the pressure difference across thediaphragm 31, which is proportional to the square of the engine speed,is equal to the pressure difference across the diaphragm 3, which isequal to the pressure difference across the metering valve l1, so thatsaid latter pressure difference is continuously maintained proportionalto the square of the engine speed.

tained constant and substantially zero by feeding the inlet of thepositive displacement pump from a second positive displacement pump ofhigher output. Figs. 4 and 5 show two arrangements embodying twin pumps,

In Fig. 4 the pump II is fed from a positive displacement pump of highercapacity than pump II. The output of pump H is fed through an orifice l2into a passage l3 as in Fig. 1 a tapping 35 being taken from theupstream side of orifice I2. The passage 13 also receives fuel directfrom pump 10 through orifice H. A deaerator I2 of conventional design isprovided for de-aeration of the fuel before it enters the pump ll andpassage IS, A spring loaded and balanced relief valve 13 isprovidedbetween the passage I3 and the inlet of pump 10, so that if the pressurein passage l3 exceeds atmospheric by more than an amount determined bythe, spring bias on valve 13 the valve opens and fuel passes frompassage l3 to the inlet of pump 10.

In Fig. 5 in addition to the relief valve 13 a second relief valve 14 isprovided. This valve has a movable member whose head is acted on by thepressure at the outlet from pump Ill and which is secured to adiaphragm, against which a spring abuts and which as shown is also actedupon by the pressure difference between the outlet of pump l I (throughpassage 35 and pipe 15) and the inlet of pump 10. The valve M willtherefore open when the pressure existing in the outlet from pump 10exceeds a predetermined relationship with the pressure in the passage35.

- Although no supercharger is shown in the drawings it will beappreciated that the invention may be embodied in a fuel supply systemfor a supercharged engine.

I claim:

1. A fuel supply system for an internal combustion engine comprising anadjustable metering value, an adjustable pressure regulating valve inseries with said metering valve, an enginedriven positive displacementpump having an outlet duct with a constriction therein located to passthe whole output of said pump, a pressureresponsive element located torespond to changes in pressure difference across said constriction,

series with said metering valve, a constriction" located in said ductbetween said pump and adjustable valves to pass the whole output of saidpump,.a pair of diaphragms one of which is located to be acted upon bythepressure difference across said constriction and the other of whichis located to be acted upon by the pressure difference across saidmetering valve. and a connection between said diaphragms whereby thepressure difference across said metering orifice is maintainedproportional'to the. pressure diiler ence across said constriction.

3. A fuel supply system for an internal com bustion engine, comprisingan engine-driven positive displacement pump for supplying fuel through aduct to said engine, an adjustable metering valve in said duct, anadjustable pressure regulating valve also in said duct, and in serieswith said metering valve, a constriction located in said duct betweensaid pump and adjustable valve to pass the whole output of said pump, apair of diaphragms one of which is located to be acted upon by thepressure difference across said constriction and the other of whichis'located to be acted upon by the pressure difference across saidmetering valve, and a pivoted lever connecting said diaphragms and alsoactuating said pressure regulating valve.

4. A fuel supply system for an internal combustion engine, comprising anengine-driven positive displacement pump for supplying fuel through aduct to said engine, an adjustable metering valve in said duct, anadjustable pressure regulating valve also in said duct, and in serieswith said metering valve, 2. constriction located in said duct betweensaid pump and adjustable valves to pass the whole output of said pump, a

pair of diaphragms one of which is located to be acted upon by thepressure difierence across said constriction and the other of which islocated to be acted upon by the pressure difference across said meteringvalve, a pivoted lever connecting said diaphragms and also actuatingsaid pressure regulating valves, and a temperature-responsive membercarrying the pivot for said lever.

5. A fuel supply system for an internal combustion engine, comprising anengine-driven positive displacement pump for supplying fuel I through aduct to said engine, an adjustable metering valve in said duct, anadjustable pressure-regulating valve also in said duct, and in serieswith said metering valve, a constriction located in said duct betweensaid pump and adjustable valves to pass the whole output of said pump, apair of diaphragms one of which is located to be acted upon by thepressure diflerence across said constriction. and the other of which islocated to be acted upon by the pressure difference across said meteringvalve, a temperature sensitive member for varying the flow area of saidconstriction, and a connection between said diaphragms, whereby thepressure difference across said metering valve is maintainedproportional to the pressure difference across said constriction.

6. A fuel supply system as claimed in claim 2. in which the positivedisplacement pump is in series with a second positive displacement-pumpwhereby the pressure difference across the first of said pumps ismaintained substantially zero.

GEORGE JEFFREY ARMSTRONG.

' REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

